Thymic output and peripheral T lymphocyte subsets in relapsing–remitting multiple sclerosis patients treated or not by IFN-β

We explored the parameters of central and peripheral tolerance in patients with stable relapsing–remitting multiple sclerosis, treated or not with IFN-β. TREC-positive T cells were lower in patients compared with controls, mainly in CD4+ subset, compatible with a thymus dysfunction or an expansion of peripheral lymphocytes. Compared to controls, the frequency of activated CD4+CD25+ T cells was higher in patients without modification of the CD4+CD25high T cell proportion. The IFN-β-treatment did not modify the TREC-positive cell frequency nor the naive/memory T cell subset percentage but was associated with lower blood lymphocyte count and a lower frequency of CD4+CD45RChigh subset.